Current finite linear motion guide units of the sort recited just above have been used extensively in relatively sliding parts in diverse fields of machinery such as semiconductor manufacturing machines, various assembling machines, and all sorts of robots. The electronic machines with the promotion of miniaturization and high performance thereof are needed increasingly to be compact, highly functional and applicable to high-speed acceleration/deceleration under high load capacity. Especially, small-sized finite linear motion guide units are needed to be applicable to high-speed acceleration/deceleration even under small-sized and high-loaded capacity and further to be easier for assembly.
In co-pending Japanese Laid-Open No 2012-202, 458, there is disclosed a finite linear motion guide unit in which the holder plate to keep the rollers between the lengthwise guideway members is made less in warp or bending in lengthwise direction and means to keep the rollers are made at the windows in the holder plate to make less the pitch between any adjacent rollers to increase the number of roller lying in a predetermined length. With the finite linear motion guide unit constructed as stated just earlier, the holder plate is made of synthetic resin and integral with a holder part to have a pinion wheel. The holder plate has more than one window to keep the rollers in the holder plate in a fashion tilting 45 degrees with respect to the side or plane of the holder plate and also any two adjoining rollers intersecting with one another. The edge defining the window has grasping parts to make engagement with the circular edges of the roller. The holder plate has flanges extending out of any side of the holder plate so as to make less the warp or bending of the holder plate.
In another co-pending Japanese Laid-Open No. 2007-232,062, there is disclosed a finite linear motion guide unit in which a mechanism to prevent any discrepancy is constituted with a pinion held in a retainer and a rack lying on the guideway member. The pinion is has a configuration rich in rigidity or stiffness. The mechanism to prevent any discrepancy constructed as stated earlier has a holder held on the pinion holder, a rack placed in a relief valley between a pair of the guideway member, and a pinion wheel provided with teeth mating with the rack and mounted for rotation on the holder. The pinion wheel has a circular plate, teeth made on the circular plate in a geometry spaced away uniformly circumferentially to mate with the rack, and a journal shaft to support for rotation the pinion wheel on the holder. The tooth has the tooth shape having a flat tooth top and tooth sides extending in parallel with each other to provide a rectangular tooth configuration having a uniform tooth thickness.
In a further another co-pending Japanese Laid-Open No. H11-108,056 (refer to literature 1 hereinafter), there is disclosed a finite linear guideway in which the teeth on the rack have recesses to prevent any interference of the teeth with the rollers while running along the track raceway. The finite linear guideway recited just above has a pair of raceway members, more than one cylindrical rolling elements lying between raceway grooves in the raceway members, a retainer plate to keep the cylindrical rollers lying between the raceway members, a rack laid in a relief groove made in the raceway groove, and a pinion wheel mating with the rack and mounted for rotation on the retainer plate. The rack has recesses each of which is made between any two adjacent teeth. Upon relative movement of the paired raceway member, even if the rolling elements roll through the raceway lying between the raceway grooves to make relative movement together with the retainer plate, the foremost ends of the cylindrical rollers only pass through the recesses of the teeth of the rack with no interference with the teeth of the rack. Moreover, with the limited linear motion guide unit having the limited linear motion guideway constructed as stated earlier, there is simply made the limited linear motion guide having a fear of causing any discrepancy.
In a further another co-pending Japanese Laid-Open No. 2003-176,820, there is disclosed a finite linear guide unit in which a rack-and-pinion arrangement is interposed between paired guide rail members to keep a retainer against falling off from the guide rail to make it possible to use the guide unit having the relief groove less in depth. This construction makes it easier to use the rack less in depth. With the finite linear guide unit constructed as stated earlier, the rack is constituted with toothed parts provided spaced away at preselected intervals, and side walls extending lengthwise continuously on both sides of the toothed parts to connect at least adjacent toothed parts with each other. The side walls of the rack are made large in thickness to broaden toward the end so as to make engagement with dovetailed wall surfaces of the relief groove inside the raceway groove of the guideway member to hold the rack inside the relief groove of the guide unit.